1. Field of the Invention
The present invention relates to a mobile communication system including base stations each having a definite number of traffic channels.
2. Description of the Related Art
In a prior art mobile communication system such as a prior art automatic private branch exchange (PBX) system, a plurality of personal handyphone system (PHS) basestations, i.e., cell stations (CSs) are connected to a switching network. In this case, in a coverage area of each of the PHS base stations, there are only three possible traffic channels where communication by speedch information and/or unrestricted digital information (UDI) is carried out. That is, three traffic channels and one signal channel are provided in one of the PHS base stations.
Note that speech information or unrestricted digital information depends upon the type of a mobile station, i.e., a person station (PS) such as a PHS cordless set.
Generally, since a speech information communication terminates in a short time, an all-busy state where all the channels of one PHS base station are occupied by speech information communications hardly continues for a long time. Therefore, if the number of installed PHS base stations is determined optimally in accordance with a call lost probability based upon speech information communications, it is possible to avoid such an all-busy state by speech information communications.
On the other hand, an unrestricted digital information communication often continues for a long time. Therefore, even if the number of installed PHS base stations is determined optimally in accordance with a call lost probability based upon speech information communications, when some of the traffic channels of one PHS base station are occupied by unrestricted digital information communications, it is impossible for speech information communication to be carried out in a coverage area of this PHS base station.